Heretofore, wheelchairs have existed wherein the chair or seat portion thereof was rockable about a common axis, or tilted about the rear apex of the seat, or which was pivotally connected to side members of a chair at a plurality of points to allow tilting thereof.
For example, U.S. Pat. No. 4,893,827 relates to a chair for use by an incapacitated person having a wheeled frame which carries a body support assembly composed of a seat, a back, and a foot rest. The back is angularly adjustable relative to the seat and the footrest is angularly adjustable relative to the seat. The body support assembly is rockable as a unit relative to the frame to enable the entire assembly to occupy any one of a number of tilted positions. The body support assembly may be removed as a unit from the frame for use as a car seat or the like.
U.S. Pat. No. 5,785,384 relates to a device for an adjustable chair where the back of the chair at a first mounting site on each side thereof is pivotally connected to respective side members of the chair and at a second mounting site forms a hinged connection with a rear part of the chair set frame, where the chair seat frame at a front mounting site on each side thereof is slidably connected to a respective side member along a front guide which forms a part of the side member. The first mounting site on the chair back is designed to slide along a rear, forward and downward inclining guide in the side member and the seat frame has on each side a rear mounting site between said front mounting site and said second mounting site for the chair back, said rear mounting site forming a slidable connection with a guide in each respective side member, which is located between the front and rear guides when seen in the longitudinal direction of the side member which is either horizontal or inclines slightly forward and upward.
U.S. Pat. No. 5,044,647 relates to a kit or assembly which can be used in the manufacture of a new wheelchair or to retrofit an existing wheelchair. The basic wheelchair structure includes a base portion having a pair of cross members mounted in the rear half of the upper portion of the wheelchair base structure. A pair of parallel guide rails are mounted between the cross members with a seat support bar attached to a pair of pillow blocks mounted on the guide rails. A linear actuator is centrally positioned within the wheelchair base structure to longitudinally move the seat support bar forwardly or rearwardly within the wheelbase of the wheelchair. A rear edge of a wheelchair seat unit is pivotally attached to the upper surface of the seat support bar. Cam plates, each having a curved cam slot, are provided on each side of the seat unit with the cam slots engaging cam followers mounted on a pair of stanchions provided on each side of the rear portion of the base structure. A control switch causes the linear actuator to move the seat support bar in a forward or rearward direction which causes the seat unit to move causing the cam follower pins positioned within the cam slots to tilt or angularly move the seat unit to a maximum reclined position of 60 degrees. The entire seat unit is moved forward a predetermined distance to obtain the desired degree of tilt and to maintain the center of gravity substantially centered within the base structure to maintain the balance and stability of the wheelchair and the safety of the patient.